Filament.



UNI-TED STATES P gEN 01 PRICE.

WILLIAM D. GGOLIDGE, OF SCHENECTADY. NEW YORK, ASSIG-NOB T1) TBIC COMPANY, A CORPORATION .OF NEW YORK.

murmur;

No Drawing.

Specification 01' Letters Patent. Patente l Nov. 14, 1911. Application filed August 1, 1906. Serial No. 828327 To all wlwm it may concern: Be it known that- I, WILLIAM D. men, a citizen of the United States, residing at fSchenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Filaments, of which the-following is a specification.

This ,invention relates to incandescent lamp filaments and particularly to filaments operative at exceedingly high temperatures.

Incandescent lamp fi aments now in common use are substantially circular in cross section, and consequently possess a relatively small surface area per unit of volume. On the other hand, fiat filamentsmay be given a surface area varying between wide limits and this variation may be made without alterin the resistance of the filament, providetf its length-remains constant. These principles have a direct bearing on the new filament hereinafter. described, for the filament hasa relatively large radiating surface per unit of volume. Such a disposition of the conductive material has particular value when-the material is Zone of the more refractory metalssuch as tungsten, molybdenum, titanium, tantulum, niobium, etc. These metals havea comparatively good conductivity, and vfilaments made therefrom must be of considerable length when of circular cross-section and arranged for operation on commercial voltages of say 110, or 220 volts. Thelength and sizeof a cylindrical filament of any refractory material are definitely fixed by three determining factors, namely, candle power of the lamp, its voltage, and its efficiency. With these three factors. fixed, the resistance is fixed, and the latter "determines the particular length and cross-sec at-ion of the filament which givesjust sufiicient area to dissipate the rated input at the selected watts per candle.

By making the filaments of the sha e hereinafter described, I am able to vary. t e length by varying the surfncearea, and um thcrebv enabled to decrease the quantity of material necessary and utilize the material of'the filament to good advantage.

In order that my invention ma v be better understood, .1 have hereinafter escribed a process for making this improved form of filament from tungsten powder, but it should be understood that other refractory materials are applicable to the process and useful relatively large surface area.

finished filament, or slit between the opposing 2 dges of the tube.

in the product. This pre; nt a plication is I however limited to the fil ial re ractory filament of the'fo rm referrel l to, and-no claim is herein made to the procedure by which No. 377,781, filed June 7, 1907.

The metal tungsten is t Ipigal of the-gen-. eral class of refractory metals and elements;

and will be usedfor illu;trative urposes. This material is obtainable in the orm of a fine powder by the reduction of tungsten trioxld with hydrogen, or with finely divided carbon or graphite. The powder so obtained is relatively no! coherent, and in general, cannot be workel into lamp filamentjs' without the applica tion of some special treatment or process for shaping the refractory powder into coherent wires. Such a process is disclosel in my application No. 316,006, filed May 9, 1906. According to that process, the re iractory tungsten powder is rubbed into a w Lll'l'l plastic amal- GENERAL sLEcgam consisting of equal arts of cadmium and mercury, the tungsten being added in the proportion of 40 per :ent. or more by weig t. The product thus obtained'may be squlrted warm through a, die or ma be otherwise manipulated. So much 0 the process there described m: y be used in the production of filaments nor -circular in crosssection, but subsequent ste )s may be different, as hereinafter set fort] l.

After obtaining ductile ires as above described, I roll them out inl ostrips having a These fiat strips may be drawn thro igh a steel, sapphire; or diamond die of t 1e proper size to curl them up into tubes. strip may be overlap ed to strengthen the limay leave a gap or 'To remove the volatile c )mponents above mentioned, I mount suitabe lengths of the strip or tube in treatin'gbul be and there subject them inoacuo or an iiert atmosphere, to the heatin action of our] ent passed therethrough. .T e current dis ;ils or vaporizes [he edges of the fractbry material 'having w-conduetivity so 03111 pt thiggpatent. may --b e afob tained' 151 the cadmium and mercury of the binding,

material; and; teginsoliddtesg .sinters' .t0-,. I

gather the pelrttc le s bf tungsten.

The relatively large s tenedwiretr tube-1t of the filament within a lsturbin the conductor.

Thefinished filgmQnts-may be strai ht or loopedendz m operative on higher vo ,tages than; (lei- 11d be nsedrwzith the, same materlal di'egqeedjirt eyljngiriqgyl wire; I consider his. ,f atu 1 mt edm ta h n 'ithe filaments consi'st if tungsten or of other re high that a relatively longv wire 'would {be necessarv if of 'clrcular:cross-section; r

I have described the squirteblemi-xture-of fage th ptw P were ;i u

7 like a .fm l'xture contalnlng of either the front or'back surface .of strip, sq that when the strip is heated by current, volatile material penfass out With ut" the arrangement of the refractory parties 'of i t M mi m n ms wyfi a n Pa of dmixifinim d -mr an or so er eent; of tungsten, but-I .0911- hat t. I. m xtyxemmax e t-gmrifl gfiiacgngjiqr elglp hgritjfdnd that I may as low as 32.5 pugs by weight of cadmilim to parts of mercury. I

Whatlelaim as new and desireatasepure by Lettersv Pgtent-qi heUnited States is;

'1. ""A tubul'a'in filament of refractdry material having a slit alpng pne side otthefiltk 2. "A tubularffilament Oftqngfste'n having a slit nlojn-gone side of the'filament. "In "witness :WheieOfi-I have hereunto set y h B thI-Q W J y 190's WILLIAM Dj.. COQLIDGE.

Witnesses: 'z' BENJAMI B. HrILL,

- GRAGEM. HAN'IGA'N '1 

